Newlib Library

The built-in AmigaOS C library is a variant of the Newlib C standard library implementation. This section describes features of Newlib which are unique to AmigaOS.

Shared Interface Pointer

Newlib is a rather unique in that it uses a shared interface pointer name INewlib (struct Interface* type). This is only a concern when you are not using the standard C startup code and opening newlib.library directly. One consequence of using a shared interface pointer is that you must specify the NP_Child tag when using IDOS->CreateNewProc() if you child process is to share the parent process' newlib context information (e.g. stdin, stdout and stderr).

Startup Code

The standard C startup code provides information on whether your application was launched from Workbench or the Shell console. Your program always starts using the standard argc and argv parameters:

int main(int argc, char **argv)

If argc is equal to zero that means the application was started from the Workbench. In this case, the argv parameter is a pointer to a struct WBStartup.

If argc is non-zero then it means the application was started from the Shell console and the normal C startup rules apply.

Standard Interfaces

The following interfaces are handled by the C startup code and are guaranteed to be present when main() is called:

• IExec
• IDOS
• IUtility

Options

extern const char *__stdiowin;

Define __stdiowin to control the default standard I/O window which will open automatically if your program needs it. The default is "CON:64/48/800/200/[CLI command name|Task name]/AUTO/CLOSE/WAIT".

extern int __unix_path_semantics;

Define to 1 to enable POSIX style path semantics which is useful when porting applications from UNIX.

DOS File Handles

Sometimes the underlying DOS file handle may be required in some special circumstances. The _get_osfhandle() function is provided in the fcntl.h header file to access DOS file handles.

The following is an example program which demonstrates the feature.

#include <proto/dos.h>
#include <stdio.h>
#include <fcntl.h>
 
int main()
{
	printf("0x%08x 0x%08x 0x%08x\n",
		(unsigned int)IDOS->Input(),
		(unsigned int)IDOS->Output(),
		(unsigned int)IDOS->ErrorOutput());
 
	printf("0x%08x 0x%08x 0x%08x\n",
		_get_osfhandle( fileno(stdin) ),
		_get_osfhandle( fileno(stdout) ),
		_get_osfhandle( fileno(stderr) ));
 
	return 0;
}

Note that this feature is available in newlib.library 53.20 and higher.